248 THE VISCERA. 



is a longitudinal ridge for attachment of the vocal cords and 

 origin of the thyroarytenoid muscles (Fig. 105, d], and at the 

 caudal end of this ridge the caudal border presents a consider- 

 able rounded notch. 



The cricoid cartilage (cartilage cricoidea) ( 3 ) has the form 

 of a seal ring with its broader part dorsad. The broad dorsal 

 part of the ring is partly embraced by the wings of the thyroid 

 cartilage (i). Its caudal border is undulating and nearly at 

 right angles to its caudocranial axis. It is connected by 

 membrane with the first tracheal ring. The cranial border is 

 oblique to the long axis and lies in a plane which passes from 

 the ventral side craniodorsad. Near the median line on each 

 side it articulates by an oblique facet with one of the two 

 arytenoid cartilages (4). Near the mid ventral line the crico- 

 thyroid ligament (5) is attached and it stretches thence to the 

 midcaudal notch of the thyroid cartilage (i). 



The outer surface presents at the middle of each side a 

 facet for articulation with the thyroid, and is marked in the 

 median dorsal line by a ridge for the posterior cricoarytenoid 

 muscle (Fig. 105, ^). 



The arytenoid cartilages (cartilage arytenoidea) (Fig. 

 104, 4) are triangular pyramids with base and sides nearly 

 equilateral triangles. One side articulates with an oblique facet 

 on the cranial border of the cricoid near the mid-dorsal line. 

 Near the opposite apex is attached the vocal cord. At the 

 lateral angle of the base is attached on its dorsal side the pos- 

 terior cricoarytenoid muscle (Fig. 105, b}, and on its ventral 

 side the thyroarytenoid (Fig. 105, d} and lateral cricoaryte- 

 noid (Fig. 105, c] muscles. The movements produced by 

 these muscles carry the arytenoid ends of the vocal cords toward 

 or from the median plane and thus open or close the glottis. 



The epiglottic cartilage (Fig. 104, 2) is flexible (fibro- 

 cartilage) and of a cordate form. It is so curved that its caudal 

 surface is convex dorsoventrally and concave from side to side. 

 It supports the epiglottis. Its cranial surface presents a slight 

 median ridge for attachment of muscles. By its base it is 

 attached to the midventral part of the cranial border of the 

 thyroid cartilage ( i ). Its position varies so that it either stands 



